Engineering Commons^™

Effects Of Perforations On Internal Cathodic Protection And Recruitment Of Marine Organisms To Steel Pipes, Alexander John Paluzzi

Theses and Dissertations

Steel monopile support structures for offshore wind turbines require protection from corrosion on their external and internal surfaces. Cathodic protection (CP) works effectively to protect the external surfaces of monopiles, but internally, byproducts from aluminum sacrificial anode CP (SACP) and impressed current CP (ICCP) induce acidification that accelerates steel corrosion. This project investigated the effects of perforations on the performance of aluminum SACP and ICCP when used inside of steel pipes. Additionally, marine growth on the external and internal surfaces of the pipes was assessed to determine if CP byproducts affect marine organism development.

Two sealed and two perforated steel …

Ti-6al-4v Β Phase Selective Dissolution: In Vitro Mechanism And Prediction, Michael A Kurtz

All Dissertations

Retrieval studies document Ti-6Al-4V β phase dissolution within total hip replacement systems. A gap persists in our mechanistic understanding and existing standards fail to reproduce this damage. This thesis aims to (1) elucidate the Ti-6Al-4V selective dissolution mechanism as functions of solution chemistry, electrode potential and temperature; (2) investigate the effects of adverse electrochemical conditions on additively manufactured (AM) titanium alloys and (3) apply machine learning to predict the Ti-6Al-4V dissolution state. We hypothesized that (1) cathodic activation and inflammatory species (H₂O₂) would degrade the Ti-6Al-4V oxide, promoting dissolution; (2) AM Ti-6Al-4V selective dissolution would occur …

Mechanisms Contributing To Hydrogen-Influenced Early Failure Of Bridge Tendons, David Dukeman

USF Tampa Graduate Theses and Dissertations

Failures in post-tensioned tendons have occurred without warning due to fractures in the high-strength steel strands. These strands are cold-drawn to increase their strength while still retaining the preferential ductile mode of fracture. Recently, a tendon failure that occurred in an upper deviation block of the I-526 James B. Edwards bridge crossing the Wando river showed signs of corrosion and potentially another method of failure, hydrogen embrittlement. One proposed source of hydrogen is through galvanic coupling that may exist between the galvanized steel duct and the steel strands. This coupling, if substantial, can promote hydrogen evolution at the steel strand's …

Mechanisms Contributing To Hydrogen-Influenced Early Failure Of Bridge Tendons, David Dukeman

USF Tampa Graduate Theses and Dissertations

Failures in post-tensioned tendons have occurred without warning due to fractures in the high-strength steel strands. These strands are cold-drawn to increase their strength while still retaining the preferential ductile mode of fracture. Recently, a tendon failure that occurred in an upper deviation block of the I-526 James B. Edwards bridge crossing the Wando river showed signs of corrosion and potentially another method of failure, hydrogen embrittlement. One proposed source of hydrogen is through galvanic coupling that may exist between the galvanized steel duct and the steel strands. This coupling, if substantial, can promote hydrogen evolution at the steel strand's …

Application Of Wavelet Analysis And Random Field In Integrity Management Of Pipelines Containing Dents And Corrosions, Junxiong Lin

Electronic Thesis and Dissertation Repository

Metal loss corrosions and dents are two major threats to the integrity of oil and natural gas pipelines. In the pipeline industry, the Fitness-For-Service (FFS) assessment is commonly employed for pipelines containing these defects. However, FFS assessment usually assumes that a defect has a simple shape, and such a simplification may significantly affect the accuracy of the assessment. Therefore, retaining the actual shapes of defects and incorporating them into the FFS assessment can improve assessment accuracy. The main objective of the present thesis is to extract key information about the sizes, directions, and shapes of corrosions and dents from the …

Hydrothermal Liquefaction (Htl) Of Lignocellulosic Biomass For Biocrude Production: Reaction Kinetics And Corrosion-Resistance Performance Of Candidate Alloys For Reactors, Haoyu Wang

Electronic Thesis and Dissertation Repository

In recent years, the rapid increase in the demand for clean energy and green chemicals as well as concerns over the supply and environmental impacts associated with fossil. resources have stimulated intensive research on conversion of bioresources, such as lignocellulosic biomass and biowaste, into energy, fuels, chemicals, and materials.

Hydrothermal liquefaction (HTL) is a unique thermochemical conversion process, particularly applicable for the conversion of wet biomass and biowaste feedstocks. Most of the biomass HTL studies are conducted in batch reactor and focus on the effects of catalysts, reaction temperature and time on production efficiency and chemical properties of the products. …

Analysis Of Ternary Chloride Salt Corrosion In High Nickel Alloys, Dimitri Madden, Gowtham Mohan

Mechanical Engineering ETDs

The United States Department of Energy seeks to improve the efficiency of concentrating solar power technologies by employing thermal energy storage with operating temperatures above 700°C. To meet these goals, the National Solar Thermal Test Facility at Sandia National Laboratories has considered the use of a ternary molten chloride salt for sensible heat storage systems. While favored for low cost, good heat transfer properties, and stability at high temperature, ternary chloride salt also exhibits high corrosive attack. Components of a chloride salt storage system would include piping, valves, tanks, pumps, receivers, and heat exchangers, which would be exposed to high …

The Study Of Corrosion On Additive-Manufactured Metals., Braydan Daniels

Electronic Theses and Dissertations

The purpose of this study was to investigate and compare the corrosion mechanisms between wrought and additive-manufactured (3D-printed) copper and stainless steel. The experimental procedure consisted of measuring the open circuit potential, electrochemical impedance spectroscopy, linear sweep voltammetry, Tafel analysis, surface topology, and scanning electron microscopy for each metal within salt water, tap water, sulfuric acid, and synthetic body fluid (excluding copper in synthetic body fluid).

Overall, printed stainless steel was more corrosion-resistant than wrought stainless steel in tap water and synthetic body fluid based on OCP, LSV, and surface topology results. Additionally, printed copper was more corrosion-resistant than wrought …

Surface Corrosion Response Of Al Alloys A383 And Aural 2 With Ce Additions In Aqueous Nacl And Salt-Fog Environments, Michael James Thompson

Masters Theses

Copper is commonly used in aluminum alloys to increase its strength by solid solution and precipitation strengthening, however, the corrosion resistance is inversely related to the amount of copper in the alloy. Over 70 percent of material used to produce aluminum alloys in the US come from recycled (secondary) alloys, many of which have a copper content of more than one percent by weight. Alloys with tightly controlled tolerances, where copper is seen as an impurity, are unable to utilize many of the recycling feedstock without adding newly processed (primary) aluminum to dilute impurities to within specifications. Primary aluminum is …

Investigation Of Oxidation And Corrosion Resistance Of Ni-Based Alloys And Stainless Steels Under Co2 Environments At Elevated Temperatures, Spencer Roy Fultineer

Graduate Theses, Dissertations, and Problem Reports

High mechanical strength integrity, high robustness towards oxidation, and high resistance to carburization under CO2 environments at elevated temperatures are usually required for metallic systems that are employed for power generation. INCONEL 625 is a nickel-based superalloy that started development in the 1950s. This material was designed with the distinct purpose of use in high-temperature and high-pressure systems. While various materials possess the physical properties to handle these conditions, the creation of IN625 addresses the need for a material to withstand the highly corrosive properties of these kinds of environments. In order to evaluate the oxidation and corrosion resistance of …

Intergranular And Pitting Corrosion Mechanisms Of Sensitized Aluminum Alloy Aa5083, Clayton Egleston

Williams Honors College, Honors Research Projects

The motivation and objectives of this project is to examine the mechanisms of intergranular corrosion (IGC) and pitting corrosion of sensitized AA5083. In this regard, different characterization techniques were used, including optical analysis of microstructure, cyclic potentiodynamic polarization with Tafel fitting, electrochemical impedance spectroscopy with electrical equivalent circuit (EEC) fitting, and potentiostatic current transient monitoring. The transition from IGC to pitting corrosion occurs when the grain boundaries become saturated with the β-phase (Mg₂Al₃). It was found that AA5083 becomes more vulnerable to pitting corrosion as the degree of sensitization increases.